Patent GB-675992-A (GB)
Title: Improvements in automatic computing apparatus, particularly for radio navigation-aiding systems
IPC: G06G7/78
Filed: 1947-03-31
Abstract: 675,992. Electric analogue calculating systems. SPERRY GYROSCOPE CO., Inc. March 31, 1947 [March 30, 1946], No. 8724/47. Class 37. [Also in Groups XXXV and XL (c)] A computor of particular value in the solution of navigational problems, such as determining the distance and bearing of one of the stations of a hyperbolic co-ordinate radio navigation system from the path-difference values derived by the receiver, operates by representing the vector quantities occurring in the mathematical equations to be solved by alternating voltages, the modulus of the vector being represented by the amplitude of the voltage and the vector angle by the phase of the voltage relative to a reference signal. Suppose in a hyperbolic radio navigation system stations are situated at O, A, and B, then the outputs of the navigator receiver at P will be respectively proportional to OP-AP and OP-BP. In one form of computor an alternating current reference voltage generator 11 feeds preset phase-shifter and alternator pairs 8-13 and 9-14 whose outputs respectively represent in phase and amplitude vectors OA, (#A) and #OB(#B). Generator 11 also feeds adjustable generator 12 whose output represents a vector #Op<SP>1</SP> (#R<SP>1</SP>) and is controlled in phase by servo-mechanism 23 and in amplitude by mechanism 22. This output as will be seen later does not normally differ considerably from that representing R, the vector OP, and it is fed to networks 15 and 16 where it is added to the voltages representing #A and #B to produce outputs representing #AP<SP>1</SP> and #BP<SP>1</SP> respectively. Detectors 5, 18, 6, and 19 connected as shown produce D.C. potentials proportional to #R<SP>1</SP>,#AP<SP>1</SP>, #R<SP>1</SP>, #BP<SP>1</SP>, which are fed in pairs to scalar difference networks 20 and 21 to produce voltage proportional to #R<SP>1</SP>-#AP<SP>1</SP> and #R<SP>1</SP>-#BP<SP>1</SP>, i.e. (OP<SP>1</SP>-AP<SP>1</SP>) and (OP<SP>1</SP>-BP<SP>1</SP>). The differences between these voltages and the receiver outputs (OP-AP) and (OP-BP) are fed back as error voltages Ea and Eb to servo mechanisms 23 and 22 respectively in such sense as to maintain #R<SP>1</SP>produced by generator 12 equal, or almost equal, to R. Scales 24 and 25 of distance and bearing may be directly driven by the mechanisms 22 and 23 to give the polar coordinates of P from O. The information may also be fed to an automatic pilot or an automatic position indicating arrangement. In a further computer (Fig. 3) the cartesian co-ordinates of the receiver position are determined although the same vector R<SP>1</SP> as in the above computer is generated and corrected to be equal to R. The generator 12 in the previous embodiment is replaced by a more complex circuit. Phase shifters 30 and 31 have outputs, respectively advanced and retarded by 45 degrees in the reference voltage phase, which are compared in phase at 36 and 37 with the output of oscillator 28 generating a frequency equal or almost equal to that of the reference generator 11. The outputs of the phase detectors 36 and 37 are proportional to the cosines of the phase angles of the oscillator voltage with respect to the reference voltage outputs of units 30 and 31 (the x and y references). Phase detectors 36 and 37 control modulators 32 and 33 so that the outputs therefrom comprise respectively the products of cos # and the x reference voltage and sin # and the y reference voltage where # is the phase difference between the output of oscillator 28 and the x reference voltage. These outputs are controlled equally in amplitude by integrating circuit 40 and combined in vector addition circuit 44 to give a vector R<SP>1</SP> used as in the previous embodiment. In the present case the error voltages Ea and Eb are applied one to control the frequency of oscillator 28 and the other the circuit 40 controlling the amplitude of the x and y vector signals applied to circuit 44. Thus R<SP>1</SP> is controlled in frequency and phase to equal R as before. Electrical quantities representing the values of the rectangular co-ordinates of P may be derived at 49 and 50 from phase detectors 45 and 46. An arrangement for producing the x and y reference voltages with accurate 90 degrees phase separation is described with reference to Figs. 4 and 6 (not shown), and an alternative device for setting in the parameters of points A and B with reference to Fig. 5. Figs. 4, 5, and 6 (not shown).